1. Field of the Invention
The present invention relates to a thin layer EL panel and more specifically to a EL panel which is suited for use in displays and the like which exhibits as long working life and can be readily manufactured.
2. Description of the Prior Art
FIG. 1 shows a previously proposed thin layer EL panel suitable for the above mentioned purpose. This arrangement includes a glass substrate 1, a transparent electrode 2 formed of In.sub.2 O.sub.3 or SnO.sub.2 , a dielectric layer 3 formed of Si.sub.3 N.sub.4 or Ta.sub.2 O.sub.5, a layer 4 of fluorescent material such as ZnS doped with Mn, a second dielectric layer 5 and rear surface electrodes 6. The latter mentioned electrodes 6 are formed by sputtering or vacuum depositing aluminum or similar conductor and subsequently photoetching the metal layer to produce the required patterning.
When a voltage is suitably impressed across the electrodes 2 and 6, portions of the fluorescent layer 4 can be induced to illuminate in a manner which produces an image.
With this arrangement, in order to prevent the infiltration of water and impurities, it is neccessary to use Si.sub.3 N.sub.4 dielectric layers 3 and 5 which exhibit a high blocking effect. However, layers made of Si.sub.3 N.sub.4 tend to induce internal stress within the device and further exhibit poor adhesive properties with respect to the other layers defining the panel. This tends to lead to "peeling-off" or interlayer separation during the manufacture of the same. This phenomenon tends to be further promoted when voltages are impressed on the panel for prolonged periods and leads to the situation wherein the panel is no longer of practical use for display purposes.
One attempt to overcome this problem is disclosed in JP-A-52-129296 (1977) wherein it is proposed to form the dielectric layers of Si.sub.3 N.sub.4 mixed with a controlled amount of SiO.sub.2. However, this measure while improving the adhesion characteristics of the layers, suffers from the drawback that the dielectric characteristics of the layer decrease with the increase in SiO.sub.2 concentration to the degree that sufficient SiO.sub.2 cannot be added in order to adequately solve the interlayer separation problem.